The Children?s Health Act of 2000 authorized the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) to serve as the lead agency for the National Children?s Study (NCS), a longitudinal cohort study intended to examine the effects of environmental influences on child health and development. A preparatory pilot study, the NCS Vanguard, was launched in January of 2009. The NCS Vanguard enrolled during pregnancy or at birth 5,630 mothers and the children born to them. NCS Vanguard study follow-up continued until December 2014. The NCS Vanguard collected information from participant interviews, self-administered questionnaires, physical and laboratory examinations, data collector observations, and biological and environmental samples. Participants were enrolled from 40 geographic locations across the United States. The NCS Vanguard evaluated different recruitment strategies, information management systems, and study management models. The information and materials collected during the NCS Vanguard will be made available to the general research community via a remoteaccess data and sample archive and access system, in fulfillment of the original study objectives.